This invention relates to the modification of the magnetic properties of materials, and in particular in respect to the performance of high-permeability magnetic materials used in anti-pilferage or article location systems.
Certain types of markers used in anti-pilferage systems or article location systems rely for their detection and recognition on the magnetic response of a component or components of the marker to an applied varying magnetic field. Desirable magnetic properties include high but well-defined magnetic permeability, low hysteresis, and well-defined response non-linearities such as are found at the approach to magnetic saturation. It is known that the physical dimensions and shapes of the magnetic components are important in determining their response and performance in the systems. The present invention is concerned with the modification and in particular the improvement of the performance of these components by surface modulations added during manufacture within the component, perhaps in conditions where it is not possible of desirable to change the main shape or dimensions of the component.